Spillway apron



Nov- 17, 1925- h T. REHBOCK SPILLWAY APRGN Filed March 50, 1925 Patented Nov. 17, 1925.

PATENT. OFFICE.

THEQDOR REHBOCK, OE KARLSRU'HE, GERMANY.

SPILLWAY AI'RON.

1 Application filed March 30, 1925. Serial No. 19,468.

To all whom it may concern: Be it known'that I, Dr. THEODOR REH- ROCK, a citizen of Germany, residing at Karlsruhe, Baden, Germany, have invented certain new and useful Improvements in Spillway Aprons (for which I have filed an application for patent in Germany,

April 10th, 1924), of which the following is .veloclty of the whole stream,

a specification.

The fall of water rushing over platforms and weirs or passing under flood-gates produces flowing-offvelocities surpassing the speed of waves, so that the water passes from the normal or flowing course to the so-called shooting state which'has a specially destructive effect on the river bed. Various means have been applied in order to lead back the shooting course of the water to the normal flowing, viz: to velocities slower than that of waves. 7

These means consist either of deepened water cushions receiving the shock of the fall, or of aprons containing several bays, a

' number of partition walls disposed in the forms above the shooting stream a surface direction of the running water parallel to each other, or a system of grill-shaped sills surmo'unting the bottom at the same height with interposed ditches. All these means serve to change the shooting current into a flowing course by transforming the considerable quantity of kinetic energy contained in the stream into thermal energy.

When the water course below the fall has a suflicient depth, these expensive constructions, which render difficult the movement of sediments, can be spared. For even on a totally smooth and even apron the water eddy with a horizontal axis transverse to the stream transforming the kinetic energy of the water by friction into'thermal energy on a short distance, so that the water in leaving the surface eddy after having lost the greatest part of its kinetic energy runs flowing with a medium speed corresponding to that of the normallyrunning stream. This has been proved by trials on models and by observation of nature. V

Local scouring out of the bottom may however be observed-in the bed below the end of the surface eddy, which do not appear in other parts of rivers or channels-with the same avera e speed. This is due to the fact that while in a normal stream the'speed in the lower part of the cross-section near the bottomis considerably less than the average "quickly as possible.

the means shown in the accompanying drawthe apron a.

Speed, owing to the continuous friction along the bed, in the water-course down-stream of the eddy the speed decreases from the bottom to the surface of the water-course, owing to the strong withdrawal of energy being produced on the surface of the stream by the eddy, so that the current velocity in the vicinity of the bed surpasses the. medium and thus produces washings-out of the bed.

The object of my invention is to remove this pernicious repartition of the current velocities from the cross-sections of the stream down-stream from the surface eddy as I attainv this object by ings, in which" Fig. 1 is a perspective view seen tip-streamof that part of a river-bed situated 'immediately down-stream a water-fall, a weir or aflood-gate and provided with the means according to the invention. Fig. 2 is a longitudinal section of a part of a river-bed comprising a water-fall and the down-stream adjacent course. Fig. 3 is a. similar longtudinal section of a part of a bed comprising a flood-gate and the upand downstream adjacent courses. Fig. 4 shows the right hand part of Figs. larged scale.

At the extreme down-stream end of the usual even apron at protecting the bed 6 immediately down-stream the fall 0, Fig. 2, or the gate d, Fig. 3, there is disposeda low roof-shaped sill e formed integrally with This sill is on the upstream side of its upper face provided with a series otteeth f with a vertical up-stream face and agently sloping down-stream face.

011 the apron a the water forms above the shooting current 9 a surface eddy h with a 2 and 3 on an en horizontal axis transverse to the stream. As

shown in Figs. 2, 3 and 4, the sill e is situated at the exit of the water from this surface eddy. Thus the rapidly flo-wing part of the stream in the vic nity of the bed 5 is by means of the toothed sill e-f gently deviated upwards. The surface velocities which connot' injure the bed are in this manner intensified, Whilst the dangerous velocities in the vicinity of the bed are correspondingly slowed down. At the same time a ground eddy i is formed below the water-course on the unprotected part of the bed 6 down-stream the apron a, the lower part of which eddy flowing just over the even the unprotected part of the bed b.

Thus the ground eddy i prevents the bed from being washed-outand even produces .alluvions near the sill e, as has been proved by numerous trials. The gently ascending streams of water flowing through the gaps between the teeth fprevent the main current from descending too rapidly to the bed and from affecting thereby the ground. The gaps also serve to let pass the sediments.

In order to lessen still more effectively the particularly pernicious excavations along the banks or side-walls is, Fig. 1, of the bed, the teeth f at both ends of the sill 6 may have a greater width and height than the other teeth f.

- flowing course Z. '2,

The line a2'-3 in Fig. 4 indicates the passage from the shooting current 9 to the Figs. 2 and 45 is the energy-line.

.What I claim as my invention and desire to secure by Letters Patent is:

1. In combination with a spillway apron, a low sill disposed at the extreme downstream end of said apron and at the exit of the water from the surface eddy formed by the water on said apron, said sill being provided with a series of teeth having a steeply inclined face directed up-stream.

2. In combination witha spillway apron, a low roof-shaped sill disposed at the extreme down-stream end of said apron and at the exit of the water from the surface eddy formed by the water on said apron,'

said sill being provided on the upstream side of its upper face with a series of teeth having a steeply inclined up-stream face and a gently sloping down-stream face.

- In testimony whereof I aflix my signature.

DR. ING. THEODOR REHBOCK. 

